Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $61.85   11.348%   $68.8687   $68.87   $68.85   $68.90  
  Purchase #2 $230.82   5.366%   $243.2058   $243.21   $243.20   $243.20  
  Purchase #3 $184.75   8.490%   $200.4353   $200.44   $200.45   $200.40  
  Purchase #4 $205.79   9.321%   $224.9717   $224.97   $224.95   $225.00  
  Purchase #5 $170.61   12.583%   $192.0779   $192.08   $192.10   $192.10  
  Purchase #6 $230.77   5.265%   $242.92   $242.92   $242.90   $242.90  
  Purchase #7 $23.35   13.499%   $26.502   $26.50   $26.50   $26.50  
  7 purchase totals = $1,107.94       $1,198.9814   $1,198.99   $1,198.95   $1,199.00